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Notice of Draft Guidance for Implementing the January 2001 Methylmercury Water Quality Criterion
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
[Federal Register: August 9, 2006 (Volume 71, Number 153)]
[Notices]
[Page 45560-45564]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr09au06-85]
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ENVIRONMENTAL PROTECTION AGENCY
[EPA-HQ-OW-2006-0656, FRL-8207-3]
Notice of Draft Guidance for Implementing the January 2001
Methylmercury Water Quality Criterion
AGENCY: Environmental Protection Agency (EPA).
ACTION: Notice of availability and request for comments.
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SUMMARY: EPA announces the availability of draft guidance for
implementing the water quality criterion for methylmercury and requests
comments on the draft guidance. The draft document provides technical
guidance to states, territories, and authorized tribes exercising
responsibility under Clean Water Act (CWA) section 303(c) on how to use
EPA's fish tissue-based methylmercury criterion recommendation in
developing their own water quality standards for methylmercury and in
implementing these standards in Total Maximum Daily Loads (TMDLs) and
National Pollutant Discharge Elimination System (NPDES) permits. The
guidance document does not impose any legally binding requirements on
any entity. It provides various technical and policy approaches to
implementing the criterion. These approaches are recommendations only.
States, territories and authorized tribes may choose to implement other
technically-sound approaches that are consistent with the CWA and EPA's
implementing regulations.
DATES: Comments must be received on or before October 10, 2006.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2006-0656, by one of the following methods:
? http://www.regulations.gov: Follow the on-line
instructions for submitting comments.
? E-mail: ow-docket@epa.gov.
? Mail: Water Docket, Environmental Protection Agency,
Mailcode: 4101T, 1200 Pennsylvania Ave., NW, Washington, DC 20460.
Please include a total of four copies.
? Hand Delivery: EPA Docket Center (EPA/DC), EPA West, Room
B102, 1301 Constitution Ave., NW., Washington, DC 20460. Please include
a total of four copies. Such deliveries are only accepted during the
Docket's normal hours of operation, and special arrangements should be
made for deliveries of boxed information.
Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2006-
0656. EPA's policy is that all comments received will be included in
the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information provided,
unless the comment includes information claimed to be Confidential Business
Information (CBI) or other information whose disclosure is restricted by
statute. Do not submit information that you consider to be CBI or otherwise
protected through http://www.regulations.gov or ow-docket@epa.gov. The
http://www.regulations.gov website is an ``anonymous access'' system, which
means EPA will not know your identity or contact information unless you
provide it in the body of your comment. If you send an e-mail comment
directly to EPA without going through http://www.regulations.gov your
e-mail address will be automatically captured and included as part of
the comment that is placed in the public docket and made available on
the Internet. If you submit an electronic comment, EPA recommends that
you include your name and other contact information in the body of your
comment and with any disk or CD-ROM you submit. If EPA cannot read your
comment due to technical difficulties and cannot contact you for
clarification, EPA may not be able to consider your comment. Electronic
files should avoid the use of special characters, any form of
encryption, and be free of any defects or viruses. For additional
information about EPA's public docket visit the EPA Docket Center
homepage at http://www.epa.gov/epahome/dockets.htm
Docket: All documents in the docket are listed in the
http://www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
[[Page 45561]]
http://www.regulations.gov or in hard copy at the Water Docket, EPA/DC, EPA
West, Room B102, 1301 Constitution Ave., NW, Washington, DC. The Public
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through
Friday, excluding legal holidays. The telephone number for the Public
Reading Room is (202) 566-1744, and the telephone number for the Water
Docket is (202) 566-2426).
Note: The EPA Docket Center suffered damage due to flooding
during the last week of June 2006. The Docket Center is continuing
to operate. However, during the cleanup, there will be temporary
changes to Docket Center telephone numbers, addresses, and hours of
operation for people who wish to make hand deliveries or visit the
Public Reading Room to view documents. Consult EPA's Federal
Register notice at 71 FR 38147 (July 5, 2006) or the EPA Web site at
http://www.epa.gov/epahome/dockets.htm for current information on
docket operations, locations and telephone numbers. The Docket
Center's mailing address for U.S. mail and the procedure for
submitting comments to http://www.regulations.gov are not affected by the
flooding and will remain the same.
FOR FURTHER INFORMATION CONTACT: Jim Pendergast, Standards and Health
Protection Division, Office of Water, (4305T), Environmental Protection
Agency, 1200 Pennsylvania Ave., NW, Washington, DC, 20460; telephone
number: 202-566-0398; fax number: 202-566-0409; e-mail address:
Pendergast.jim@epa.gov.
SUPPLEMENTARY INFORMATION:
I. General Information
A. Does this Action Apply to Me?
Entities potentially interested in today's notice are those that
discharge or release mercury and methylmercury to surface waters, and
federal, state, tribal, and local authorities that regulate
methylmercury levels in surface water. Categories and entities
interested in today's notice include but are not limited to:
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Examples of potentially
Category affected entities
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State/Local/Tribal Government............. States, municipalities,
tribes.
Industry.................................. Mining, coal-fired power
generation, other
industries using mercury in
their processing
------------------------------------------------------------------------
This table is not intended to be exhaustive. Other types of
entities not listed in the table may also be interested.
B. What Should I Consider as I Prepare My Comments for EPA?
1. Submitting CBI. Do not submit this information to EPA through
http://www.regulations.gov or e-mail. Clearly mark the part or all of the
information that you claim to be CBI. For CBI information in a disk or
CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as
CBI and then identify electronically within the disk or CD ROM the
specific information that is claimed as CBI). In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2.
2. Tips for Preparing Your Comments. When submitting comments,
remember to:
? Identify the docket number and other identifying
information (subject heading, Federal Register date and page number).
? Follow directions--The agency may ask you to respond to
specific questions or organize comments by referencing a Code of
Federal Regulations (CFR) part or section number.
? Explain why you agree or disagree; suggest alternatives
and substitute language for your requested changes.
? Describe any assumptions and provide any technical
information and/or data that you used.
? If you estimate potential costs or burdens, explain how
you arrived at your estimate in sufficient detail to allow for it to be
reproduced.
? Provide specific examples to illustrate your concerns, and
suggest alternatives.
? Explain your views as clearly as possible, avoiding the
use of profanity or personal threats.
? Make sure to submit your comments by the comment period
deadline identified.
II. Background and Today's Action
A. What Is Methylmercury and Why Are We Concerned About It?
Mercury occurs naturally in the earth's crust and cycles in the
environment as part of both natural and human-induced activities. The
amount of mercury mobilized and released into the biosphere has
increased since the beginning of the industrial age. Most of the
mercury in the atmosphere is elemental mercury vapor, which circulates
in the atmosphere for up to a year, and, hence, can be widely dispersed
and transported thousands of miles from sources of emission. Most of
the mercury in water, soil, sediments, plants, and animals is in the
form of inorganic mercury salts and organic forms of mercury (e.g.,
methylmercury). Methylmercury most often results from microbial
activity in wetlands, the water column, and sediments and is the form
of mercury that presents the greatest risk to human health. Divalent
mercury, when bound to airborne particles, is readily removed from the
atmosphere by precipitation and is also dry deposited. Even after it
deposits, mercury commonly returns to the atmosphere either as a gas or
associated with particles, and redeposits elsewhere. As mercury cycles
between the atmosphere, land, and water, mercury undergoes a series of
complex chemical and physical transformations, many of which are not
completely understood.
Exposure to methylmercury can result in a variety of health effects
in humans. Children who are exposed to low concentrations of
methylmercury prenatally might be at risk of poor performance on
neurobehavioral tests, such as those measuring attention, fine motor
function, language skills, visual-spatial abilities, and verbal memory.
(NRC 2000, USEPA 2002, USEPA 2005). The primary route by which the U.S.
population is exposed to methylmercury is through the consumption of
fish containing methylmercury. For most people, methylmercury exposure
from consumption of fish and shellfish is not a health concern. Yet,
the exposure levels at which neurological effects have been observed in
children can occur via maternal consumption of fish (rather than high-
dose poisoning episodes) (USEPA 2005). The risks from methylmercury in
fish and shellfish depend on the amount of fish and shellfish eaten and
the levels of methylmercury in the fish and shellfish. Therefore, the
Food and Drug Administration (FDA) and the Environmental Protection
Agency (EPA) are advising women who may become pregnant, pregnant
women, nursing mothers, and young children to avoid some types of fish
and eat fish and shellfish that are lower in methylmercury. You can
find more information about this joint Federal advisory on EPA's Web
site at http://www.epa.gov/waterscience/fish.
In 2000, the National Academy of Sciences (NAS)/National Research
Council (NRC) reviewed the health studies on methylmercury (NRC 2000).
In its review of the literature, NRC found neurodevelopmental effects
to be the most sensitive endpoints and appropriate for establishing a
[[Page 45562]]
methylmercury Reference Dose (RfD) (NRC 2000). EPA defines an RfD as
``an estimate (with uncertainty spanning perhaps an order of magnitude)
of a daily oral exposure to the human population (including sensitive
subgroups) that is likely to be without an appreciable risk of
deleterious effects during a lifetime. On the basis of the NRC report,
EPA established an RfD of 0.0001 mg/kg per day (0.0001 milligram of
methylmercury per day for each kilogram of a person's body mass) in
2001 (USEPA 2002). EPA believes that exposures at or below the RfD are
unlikely to be associated with appreciable risk of deleterious effects.
It is important to note, however, that the RfD does not define an
exposure level corresponding to zero risk; methylmercury exposure near
or below the RfD could pose a very low level of risk that EPA deems to
be non-appreciable. It is also important to note that the RfD does not
define a bright line, above which individuals are at risk of adverse
effects (USEPA 2005). NAS determined that EPA's RfD ``is a
scientifically justified level for the protection of public health.''
With regard to other health effects of methylmercury, some recent
epidemiological studies in men suggest that methylmercury is associated
with a higher risk of acute myocardial infarction, coronary heart
disease, and cardiovascular disease in some populations. Other recent
studies have not observed this association. The studies that have
observed an association suggest that the exposure to methylmercury
might attenuate the beneficial effects of fish consumption (USEPA
2005). There also is some recent evidence that exposures of
methylmercury might result in genotoxic or immunotoxic effects. Other
research with less corroboration suggests that reproductive, renal, and
hematological impacts could be of concern. There are insufficient human
data to evaluate whether these effects are consistent with
methylmercury exposure levels in the U.S. population (USEPA 2005).
B. What Is the Current Methylmercury Criterion?
In a January 8, 2001, Federal Register notice (66 FR 1344), EPA
announced the availability of its recommended water quality criterion
for methylmercury. The methylmercury water quality criterion is derived
from the methylmercury RfD (described above) and data about the target
population to be protected (i.e., exposure parameters and assumptions).
The equation for calculating the methylmercury fish tissue residue
water quality criterion for the protection of human health is:
[GRAPHIC]
[TIFF OMITTED]
TN09AU06.006
Where:
TRC = Fish tissue residue criterion (mg methylmercury/kg fish
tissue) for freshwater and estuarine fish and shellfish
RfD = Reference Dose (based on non-cancer human health effects). For
methylmercury the RfD is 0.0001 mg/kg BW-day (0.1 ug/kg BW-day)
RSC = Relative source contribution (subtracted from the RfD to
account for marine fish consumption) estimated to be 2.7 x 10-5 mg/
kg BW-day
BW = Human body weight default value of 70kg (for adults)
FI = Fish intake at trophic level (TL) i (i = 2, 3, 4); total
default intake is 0.0175 kg fish/day for general adult population.
Trophic level breakouts for the general population are: TL2 = 0.0038
kg fish/day; TL3 = 0.0080 kg fish/day; and TL4 = 0.0057 kg fish/day.
This equation and all values used in the equation are described in
Water Quality Criterion for the Protection of Human Health,
Methylmercury (USEPA 2001b). This equation is essentially the same
equation used in the 2000 Human Health Methodology to calculate a water
quality criterion for a pollutant that may cause non-cancer health
effects, but is rearranged to solve for a protective concentration in
fish tissue rather than in water. Thus, the equation does not include a
bioaccumulation factor (BAF) or drinking water intake value
(methylmercury exposure from drinking water is negligible (USEPA
2001a)). Incorporating the relevant values into the above equation, EPA
obtained a fish tissue concentration (TRC) of 0.3 mg methylmercury/kg
fish as the concentration in fish tissue that should not be exceeded.
EPA's preference is for states and authorized tribes to use local or
regional consumption rates, if these would better reflect the target
populations.
C. What Is The Draft Implementation Guidance?
In the 2001 Federal Register notice of the availability of EPA's
recommended water quality criterion for methylmercury, EPA stated that
it would develop associated procedures and guidance for implementing
the criterion. We are issuing that draft guidance today. The guidance
will assist states in developing a water quality criterion for
methylmercury in their water quality standards. States can either adopt
EPA's recommended criterion or another criterion that is scientifically
defensible and consistent with the Act and its implementing
regulations. 40 CFR 131.11(a)(2).
This guidance document presents suggested approaches to criteria
adoption and implementation. These approaches are recommendations and
do not represent the only technically defensible approaches. The
discussion in the guidance document is intended solely as guidance.
This guidance does not change or, substitute for, applicable sections
of the CWA or EPA's regulations; nor is it a regulation itself. Thus,
it does not impose legally binding requirements on EPA, states,
authorized tribes, or the regulated community and may not apply to a
particular situation. EPA, state, territorial, and tribal decision
makers retain the discretion to adopt approaches on a case-by-case
basis that differ from this guidance where appropriate.
D. Why Did EPA Draft This Guidance?
The methylmercury criterion is expressed as a fish and shellfish
tissue value, and this raises both technical and programmatic
implementation questions. EPA expects that, as a result of the revised
methylmercury water quality criterion, together with a more sensitive
method for detecting mercury in effluent and the water column, and
increased monitoring of previously unmonitored waterbodies, the number
of waterbodies that states report on CWA section 303(d) lists as
impaired due to methylmercury contamination might continue to increase.
Development of water quality standards, NPDES permits, and TMDLs
present challenges because these activities typically have been based
on a water concentration (e.g., as a measure of mercury levels in
effluent). This guidance addresses issues associated with states and
authorized tribes adopting the new water quality criterion into their
water quality standards programs and implementation of the revised
water quality criterion in TMDLs and NPDES permits. Further, because
atmospheric deposition serves as a large source of mercury for many
waterbodies, implementation of the criterion involves coordination
across various media and program areas.
E. What Does the Draft Guidance Recommend?
For states and authorized tribes exercising responsibility under
CWA section 303(c), this document provides technical guidance on how
they might want to use the recommended 2001 fish tissue-based criterion
to develop their own water quality standards for
[[Page 45563]]
methylmercury. States and authorized tribes may decide to adopt the EPA
recommended methylmercury fish tissue-based criterion based on the
national default fish consumption rate or translate the tissue value to
a water column value through use of methylmercury BAFs. If a state or
authorized tribe decides to translate the fish tissue criterion to a
water column criterion, EPA recommends three approaches for relating a
concentration of methylmercury in fish tissue to a concentration of
methylmercury in ambient water: (1) Deriving site-specific
methylmercury BAFs; (2) using bioaccumulation models; and (3) using
EPA's draft default methylmercury BAFs. All three approaches have
limitations, such as the amount of data necessary to develop a BAF.
This guidance discusses the advantages and limitations of each approach.
States and authorized tribes may also consider calculating their
own fish tissue criteria or adopting site-specific criteria for
methylmercury to reflect local or regional fish consumption rates or
relative source contributions. This guidance also discusses variances
and use attainability analyses relating to methylmercury.
This document describes analytical methods for determining the
concentrations of mercury and methylmercury in both tissue and water.
These methods can detect mercury and methylmercury in tissue and water
at very low levels--well below the levels of the previous criterion for
mercury in the water column and the current criterion of methylmercury
in fish tissue. This document also provides guidance for field sampling
plans, laboratory analysis protocols, and data interpretation that is
based on previously published EPA guidance on sampling strategies for
contaminant monitoring. This guidance also describes how states can
assess the attainment of water quality criteria and protection of
designated uses by comparing sampling data to water quality criteria.
This guidance also discusses approaches for the development of
TMDLs for waterbodies impaired by mercury. This includes approaches for
TMDLs for waterbodies where much of the mercury is from atmospheric
sources and suggestions regarding how such TMDLs can take into account
ongoing efforts to address sources of mercury, such as programs under
the Clean Air Act (CAA) and pollution prevention activities.
EPA's Technical Support Document for Water Quality-based Toxics
Control (TSD), EPA 505/2-90-001, explains how to implement criteria
expressed in terms of pollutant concentrations in water in NPDES
permits. States that decide to implement the methylmercury tissue
criterion as a water concentration for NPDES permits should continue to
use the TSD guidance. However, for states that decide to implement the
methylmercury tissue criterion directly, that is, without translating
it into a water column value, the TSD doesn't provide relevant
guidance. Today's draft guidance also includes a recommended approach
for directly incorporating the methylmercury tissue criterion in NPDES
permits.
F. Are There Particular Issues on Which EPA is Requesting Comment?
EPA requests comments only on the draft methylmercury criterion
implementation guidance. EPA is not requesting comments on the 2001
methylmercury criterion itself. Although EPA solicits comment on the
entire draft guidance, it is particularly interested in the following
topics:
1. Implementation Approach for NPDES Permits Where the Criterion Is
Implemented as a Fish Tissue Value
Today's guidance presents a recommended approach for directly
incorporating the methylmercury tissue criterion in NPDES permits. This
approach does not rely upon a state developing a bioaccumulation factor
to convert the methylmercury tissue criterion into a water
concentration equivalent. The approach recommends that facilities that
use, accept or receive mercury into their wastewaters develop mercury
minimization plans. For discharges that are small contributors of
mercury to a watershed or do not use mercury in their processes, the
approach recommends that current permit effluent levels remain
constant. EPA expects that most facilities will fall into this category
due to significant loadings from other sources (e.g., air deposition,
abandoned mines). For discharges that are significant contributors of
mercury to a watershed and use mercury in their processes, the approach
recommends that permit effluent limits ensure the attainment of water
quality standards. EPA expects that few dischargers should fall into
this category. For new or increased discharges, the approach recommends
that permit effluent limits hold watershed loadings constant using
antidegradation principles.
EPA solicits comment on the recommendations for directly
incorporating the methylmercury tissue criterion in NPDES permits. The
draft guidance recommends that a permitting authority could reasonably
conclude that reasonable potential exists if two conditions are present
(1) The NPDES permitted discharger has mercury in its effluent at a
quantifiable level and (2) fish tissue from the waterbody into which
the discharger discharges exceeds the fish tissue water quality
criterion. EPA specifically solicits comment on alternate methods,
based on using other information, for determining that there is
reasonable potential to exceed the water quality standard where fish
tissue data show that the methylmercury tissue criterion in a water
quality standard is achieved.
2. Applying Water Quality Variances on a Watershed or State-Wide Basis
Traditionally, states establish water quality variances that are
specific to a pollutant and a facility. EPA recognizes that, for
mercury, there are situations where a number of NPDES dischargers are
located in the same area or watershed and the justification supporting
granting a variance applies to all of the dischargers. Two states, Ohio
and Michigan, have already developed variances that apply to multiple
discharges for mercury. Today's guidance encourages states and
authorized tribes to consider establishing a multiple-discharger
variance for a group of dischargers collectively.
EPA solicits comment on whether it should discuss multi-discharge,
watershed, or state-wide variances in the final guidance.
G. References Cited
NRC (National Research Council). 2000. Toxicological effects of
methylmercury. Committee on the Toxicological Effects of
Methylmercury. National Academy Press. Washington, DC.
USEPA (U.S. Environmental Protection Agency). 1991. Technical
Support Document for Water Quality-based Toxics Control. EPA 505/2-
90-001. U.S. Environmental Protection Agency, Office of Water
Enforcement and Permits and Office of Water Regulations and Standards.
USEPA (U.S. Environmental Protection Agency). 2001a. Water quality
criteria: Notice of Availability of water quality criterion for the
protection of human health: Methylmercury. U.S. Environmental
Protection Agency, Office of Water, Washington, DC. Fed. Regist., 66:1344.
USEPA (U.S. Environmental Protection Agency). 2001b. Water quality
criterion for the protection of human health: Methylmercury. EPA-
823-R-01-001. U.S. Environmental Protection Agency, Office of Water,
Washington, DC.
USEPA (U.S. Environmental Protection Agency). 2002. Integrated Risk
Information System (IRIS). Methylmercury. U.S. Environmental
Protection Agency, Office
[[Page 45564]]
of Research and Development, National Center for Environmental Assessment.
USEPA (U.S. Environmental Protection Agency). 2005. Regulatory
Impact Analysis of the Clean Air Mercury Rule. Final Report. EPA-
452/R-05-003. U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, Air Quality Strategies and Standards
Division, Research Triangle Park, NC.
Dated: August 3, 2006.
Benjamin H. Grumbles,
Assistant Administrator for Water.
[FR Doc. 06-6803 Filed 8-8-06; 8:45 am]
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